When I build a full prototype bot in the future, I will more than likely use 8 rollers per wheel for better traction.
Shown on the right, the mecanum wheel is made of parts from vexlabs.com. The non-competition-legal parts are the white 1/2" nylon spacers.
Actually, as shown that mecanum wheel is FVC legal. VexLabs sells 1/2" nylon spacers (link) and by using a file and a poorman’s lathe (aka drill ;)) you can file the curve into them.
I was under the impression that if it did not come specifically in the VEX starter kit then it is not competition legal?
mostly everything from vexlabs is completely legal for competition unless it says that it is not on the website or in the rules
Well that’s nice to know. Even though it’s part of a spacer “set” it’s still cheaper to get them through vexlabs than home depot, lowes, Ace, Target, or Walmart. They’re also softer, easier to file, and get better traction than those at the places above.
:ahh: methinks you will have a really long (if not hard) time making 64 perfect rollers (2 per roller, 8 rollers per wheel, 4 wheels on the bot).
vivek
the local college by us has a CNC lathe that would be able to make 64 perfect rollers… That would be awesome.
By hand would be much harder. Is that how you made them?
When can we expect to see a working chassis?
when i made my vex meccanum wheels those were the most time consuming part by drilling them out and to assemble them
Yes, I used a variable-speed drill and a file that has 4 different surfaces to file them down. They’re not perfect, but to file 10 of them it took ~45 minutes.
To drill through the metal pieces it took 10 minutes since I came up with a way to do them all at once.
I bent the metal by hand so it’s not exactly 45 degree, and the spacing on the rollers isn’t exact either. It’s a concept though, to show that it can be done.
If you have access to machine tools you can probably make a dye (or is it die?) out of steel so you can bend them all exactly 45.
Unfortunately, IFI will not break up the $8 kit that comprises of the plastic (and adjustable) lock bars. To complete a single set of wheels with this design, one would have to spend $48 for these parts alone. Before those, the price per wheel would be $14 per wheel with 8 rollers.
Why can’t you just buy the same nylon spacers at your local hardware store? Would then only cost about $32… depending on how much each one costs. Some stores vary, the one I work at has them around $0.35 each… I can get them at about a dime a piece or less after discount.
Well since many people are showing their vex mecanums, I might as well show what I am up to…
http://img508.imageshack.us/img508/7692/mecanumtype1gr3.png
The wheels are roughly the same size as the 4" wheels. Uses eight 2" lengths of vex shaft and 16 shaft collars per wheel.
I hope to have these wheels done soon.
He is referring to the “lock bars” that make the wheel spin with the axle, not the spacers.
Kit ($8):
http://www.vexlabs.com/images/vex-robotics-starter-kit/2016.gif
http://www.vexlabs.com/vex-robotics-starter-kit-parts.shtml
Oh… heh, thanks. But Vexlabs has all metal lockbars that work 10x better and are sold in 8 or 4 packs…
You could use the metal lock bars, however you’d run into a problem when lining things up with the axle since most supports are not 90 degrees to the axle. I need the plastic ones since they are adjustable.
Edit: You don’t run into this problem with FRC mecanums because the axles are round whereas VEX are square.
Are those white nylon spacers your rollers? Just wondering, why are they so tiny?
About the curvature of the rollers, my team (FRC) built a set of custom mecanums last summer and we were originally going to CNC lathe the rollers, but we realized that rubber labstops were almost the same shape, squishy enough to conform to the floor, and much cheaper. They might not behave as well at the VEX scale though, I wouldn’t know.
Rachal –
Keeping the VEX mecanum wheels into the realm of “competition legal” is pretty tough when it comes to designing the rollers. The link that lavery posted way back up in the thread seems pretty solid for traction, but I have fairly limited tools at my house and can’t cut into the metal like that with any accuracy.
Alot of the “heat shrink” that’s floating around and “molding” that’s floating around concerning VEX tells me people are trying to craft their rollers themselves out of non-VEX materials, which isn’t competition legal.
When I get home, I’ll update the pic with pricing, including what part #'s you have to purchase from vexlabs and then a price breakdown including what spare parts are leftover.
